As such a cylindrical case described above, a cylindrical case disclosed, for example, in Patent Document 1 is known. This cylindrical case is a fan case covering fan blades of an aircraft jet engine, and includes an intermediate casing and an extension connected to the engine rear side of the intermediate casing.
The extension includes a cylindrical joining shell arranged on the engine front side, and a downstream end arranged on the engine rear side. The downstream end is formed by annularly connecting a plurality of angular sectors, and in a state that the angular sectors are connected annularly, an annular groove for connecting nacelle covers is formed.
The downstream end is formed by arranging two types of angular sectors alternately. An angular sector made of an Al alloy is arranged at a position where the level of reverse thrust transmitted by the nacelle covers is relatively low, while an angular sector made of a wear-resistant Ti alloy is arranged at a position where the level of reverse thrust transmitted by the nacelle covers is higher.
In this case, both the two types of angular sectors are connected to an end of the joining shell by fixing outward flanges formed on both the joining shell and the angular sectors to each other with screws in the axial direction.